Hi,
Am Dienstag, den 18.04.2017, 18:34 +0000 schrieb Peter Maloney:
> The 'slower with every snapshot even after CoW totally flattens it'
> issue I just find easy to test, and I didn't test it on hammer or
> earlier, and others confirmed it, but didn't keep track of the
> versions. Just make an rbd image, map it (probably... but my tests
> were with qemu librbd), do fio randwrite tests with sync and direct
> on the device (no need for a fs, or anything), and then make a few
> snaps and watch it go way slower.
>
> How about we make this thread a collection of versions then. And I'll
> redo my test on Thursday maybe.
I did some tests now and provide the results and observations here:
This is the fio config file I used:
<rbd.fio>
[global]
ioengine=rbd
clientname=admin
pool=images
rbdname=benchmark
invalidate=0 # mandatory
rw=randwrite
bs=4k
[rbd_iodepth32]
iodepth=32
</rbd.fio>
Results from fio on image 'benchmark' without any snapshots:
rbd_iodepth32: (g=0): rw=randwrite, bs=4K-4K/4K-4K/4K-4K, ioengine=rbd,
iodepth=32
fio-2.16
Starting 1 process
rbd engine: RBD version: 0.1.10
Jobs: 1 (f=1): [w(1)] [100.0% done] [0KB/3620KB/0KB /s] [0/905/0 iops]
[eta 00m:00s]
rbd_iodepth32: (groupid=0, jobs=1): err= 0: pid=14192: Thu Apr 20
13:11:27 2017
write: io=8192.0MB, bw=1596.2KB/s, iops=399, runt=5252799msec
slat (usec): min=1, max=6708, avg=173.27, stdev=97.65
clat (msec): min=9, max=14505, avg=79.97, stdev=456.86
lat (msec): min=9, max=14505, avg=80.15, stdev=456.86
clat percentiles (msec):
| 1.00th=[ 26], 5.00th=[ 28], 10.00th=[ 28],
20.00th=[ 30],
| 30.00th=[ 31], 40.00th=[ 32], 50.00th=[ 33],
60.00th=[ 35],
| 70.00th=[ 37], 80.00th=[ 39], 90.00th=[ 43],
95.00th=[ 47],
| 99.00th=[ 1516], 99.50th=[ 3621], 99.90th=[ 7046], 99.95th=[
8094],
| 99.99th=[10159]
lat (msec) : 10=0.01%, 20=0.29%, 50=96.17%, 100=1.49%, 250=0.31%
lat (msec) : 500=0.21%, 750=0.15%, 1000=0.14%, 2000=0.38%,
>=2000=0.85%
cpu : usr=31.95%, sys=58.32%, ctx=5392823, majf=0, minf=0
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=100.0%,
>=64=0.0%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%,
>=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.1%, 64=0.0%,
>=64=0.0%
issued : total=r=0/w=2097152/d=0, short=r=0/w=0/d=0,
drop=r=0/w=0/d=0
latency : target=0, window=0, percentile=100.00%, depth=32
Run status group 0 (all jobs):
WRITE: io=8192.0MB, aggrb=1596KB/s, minb=1596KB/s, maxb=1596KB/s,
mint=5252799msec, maxt=5252799msec
Disk stats (read/write):
vdb: ios=6/20, merge=0/29, ticks=76/12168, in_queue=12244, util=0.23%
sudo fio rbd.fio 2023.87s user 3216.33s system 99% cpu 1:27:31.92
total
Now I created three snapshots of image 'benchmark'. Cluster became
iresponsive (slow requests stared to appear), a new run of fio never
got passed 0.0%.
Removed all three snapshots. Cluster became responsive again, fio
started to work like before (left it running during snapshot removal).
Created one snapshot of 'benchmark' while fio was running. Cluster
became iresponsive after few minutes, fio got nothing done as soon as
the snapshot was made.
Stopped here ;)
Regards,
--
J.Hofmüller
mur.sat -- a space art project
http://sat.mur.at/
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